1. Field of the Invention
The present invention relates to a clamping system and a clamping method.
2. Description of the Related Art
In a clamping system, where the degree of parallelism between a movable die plate and a fixed die plate cannot be held, the dimensional error of the product becomes larger, burrs easily occur, and other problems arise. Therefore various techniques for keeping the degree of parallelism between a movable die plate and a fixed die plate have been proposed. For example, Japanese Patent Publication (A) No. 2004-322609 discloses a technique of providing a plurality of ball screws for moving the movable die plate in a die opening and closing direction on the peripheries of the movable die plate and the fixed die plate along the tie bars and individually controlling the drive operations of these plurality of ball screws so as to perform the clamping while maintaining the degree of parallelism between the die plates. Note that, although not concerning the degree of parallelism of die plates, a technique of detecting a location of a piston for clamping provided on the tie bar is known (for example, Japanese Patent Publication (A) No. 2004-001470).
In the technique of Japanese Patent Publication (A) No. 2004-322609, the degree of parallelism between die plates is adjusted from the start of clamping to the die contact. In the clamping system, however, sometimes the degree of parallelism between die plates is degraded even during the period after the die contact to the completion of clamping.